1. Field
The present disclosure relates to a genetically engineered and acid-resistant yeast cell with enhanced activity of radiation sensitivity complementing kinase and a method of producing lactate by using the yeast cell.
2. Description of the Related Art
Organic acids are widely used in a variety of industries. For example, lactate is an organic acid that is used in a variety of industrial fields, including food, pharmaceutical, chemical, and electronic industries. Lactate is a colorless, odorless, water-soluble, low-volatile material. Lactate is also not toxic to the human body, and is used as a flavoring agent, a sour taste agent, a preserving agent, or the like. Lactate is also used as a source of polylactic acid (PLA) that is an environmentally friendly, biodegradable plastic known as an alternate polymeric material.
Organic acids may be dissociated into hydrogen ions and their own negative ions at a higher pH than their own dissociation constant (pka value), for example, under a neutral condition. Meanwhile, organic acids, for example, lactic acid, may be present in the form of free acid without an electromagnetic force at a pH lower than its own pKa value. An organic acid in the form of negative ions may not be permeable with respect to a cell membrane, but may be permeable with respect to the cell membrane when it is present in the form of free acid. Therefore, an organic acid in free acid form may flow into the cells from extracellular environments where the concentration of the organic acid is high, and thus lower an intercellular pH level. Meanwhile, an organic acid present as negative ions requires an additional isolation process involving the addition of a salt. Also, a cell lacking acid-resistance may become inactive and die under acidic conditions, such as in the case of lactic acid.
Therefore, there is a need for a microorganism with acid-resistance.